Ten-electron systems have a particular significance
because of the importance of many of them in the atmosphere of the Earth, solar system planets and exoplanets.
Clearly the ab initio  solution for molecules, belonging to this second
group require greater computational efforts and remains much further
from a satisfactory or final solution, than the molecules belonging
to the two-electron group. The ab initio  predictions of the ro-vibrational
energy levels of water reached the 1 cm\(^{-1}\)  level in [1]} and
0.1 cm\(^{-1}\)  for stretching states in [2]}, rising to
0.3 cm\(^{-1}\)  when highly excited bending modes are considered.
However, there are still many improvements need to reach
the level of accuracy achieved by Wolniewicz for H\(_2\)  calculations
[3]}, [4]}.
